9999888781 has 2 divisors, whose sum is σ = 9999888782. Its totient is φ = 9999888780.

The previous prime is 9999888751. The next prime is 9999888817. The reversal of 9999888781 is 1878889999.

Together with next prime (9999888817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7415793225 + 2584095556 = 86115^2 + 50834^2 .

It is a cyclic number.

It is not a de Polignac number, because 9999888781 - 2⁷ = 9999888653 is a prime.

It is a super-2 number, since 2×9999888781² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 9999888698 and 9999888707.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9999888751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4999944390 + 4999944391.

It is an arithmetic number, because the mean of its divisors is an integer number (4999944391).

Almost surely, 2^9999888781 is an apocalyptic number.

It is an amenable number.

9999888781 is a deficient number, since it is larger than the sum of its proper divisors (1).

9999888781 is an equidigital number, since it uses as much as digits as its factorization.

9999888781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 188116992, while the sum is 76.

The square root of 9999888781 is about 99999.4439034538. The cubic root of 9999888781 is about 2154.4267028665.

The spelling of 9999888781 in words is "nine billion, nine hundred ninety-nine million, eight hundred eighty-eight thousand, seven hundred eighty-one".